Plugging strata in boreholes



Patented Mar. `13, 19.45

oFFlc-E PLUGGING s'mA'rA nv BoaEHoLEs Newton B. Disniukes, Houston, Tex.,

Standard Oil Development Company, a corporation of Delaware Application December .6, 1941, Serial No. 421,872

1 Claim.

'I'he present invention may be briy described as involving the removing of the lter cake from the face of the formation being treatedconcurrently with the injection of treating. agents into the formation.

In the drilling of wells it is usual to employ a drilling uid, which is a suspension of finely divided solids in a liquid base, to carry the cuttings from the bottom of the bore hole, to exert sufficient pressure on the formation penetrated to prevent the flow of fluid from formations into the bore ,hole, and to form a filter cake on vthe walls of the bore hole in orderto prevent the exchange of uid between the bore hole and the penetrated formations. This drilling fluid is almost invariably present in the bore holes durin?.r the completion and reworking of wells and, as stated above, oneV of the functions of drilling fluid is to build a filter cake or the wall of the bore hole.

Heretofore, when injecting chemical sealing agents or other treating agents into selected strata of bore holes,it has been customary to' simply pack off. thev desired strata, so that vthe sealing agent maybe directed thereto, and the mud sheath on (Cl. 16S-21) l packer I3 arranged below stratum Il. The upper part of the 'well is provided with a surface string of casing 8 to which is attached a conventional well head diagrammatically shown as cap 9 having a drawoff line l0. Drill pipe' I5 is slidably arranged in the well. The lower end agent then placed in the bore hole under sulcient pressure to force it into the desired formation. It has been found that this conventional procedure has often resulted in unsatisfactory penetration because of the mud sheath, whichl reduces the rate and amount of flow of fluid from.

the bore hole into the formation.

In accordance with the present invention these of the drill pipe is provided with a wire brush I6 arranged to remove the wall of the bore hole.

A treating agent in fluid form is pumped down drill pipe Il', to a point adjacent formation il and suiiicient pressure exerted upon the treating uid to overcome the pressure present in formation Il. As the treating fluid is being forced intoA the bore hole under pressure, brush I6 is given both rotary and vertically reciprocating motion in order to clean the mud `sheath from the wall of the bore hole. The step of cleaning the plastering solids from the'sbore hole insures a prompt and thorough penetration of the treating agent therein. As stated previously, if desired, a cleaning step may be carried out before the treating agent is forced into the bore hole.

An alternative method of practicing the, present invention is shown by Fig. 2. The arrange'- ment here is similar to that of Fig. .1 with the, exception that drill stem I5 is provided with a conventional wall reamer I1. Reanier i1 is utilized to remove the mud sheath from the bore hole ancl to prevent the deposition of plastering materials on the wall of the -bore hole during the injection of the fluid treating agent into formation Il by the operation of the reamer simultaneously with the injection of sealing materiaL-into the bore hole.

Another modification of the present invention is illustrated in Fig. 3. In this embodito or concurrently with, or both prior to and concurrently with the step of forcing the treating agent irto the strata. The cleaning step-insures a substantially greater penetration of theagents into the strata.'

Other objects and advantages of the presentA invention may be seen from a reading of the following description taken in conjunction with the drawing in which l Figs. 1, 24 and 3 are fragmentary views illustrating several modifications in the practice of tle present invention` One of the methods of carrying out the present invention is illustrated in Fig. 1 which is a fragmentaryview showing a section of a bore hole. In Fig. 1 it is desired to inject a chemical sealing agent into stratum Il. In order to carry available liquid, such as water, rdown through out this step, the bore hole l2 is provided with a 55 ment, a jet lI8 is attached to the lower end of drill vstem i5 so that the jetmay be directed on the wallv of the bore hole, thereby removing foreign matter therefrom. In utilizing this embodiment, itis preferred to first vforce a readily the drill pipe to remove the mud cake from the wall of the bore hole, and follow this with a charge of 'fluid treating agent, utilizing the agent as; the liquid to be jetted against the formation to remove foreign matter-therefrom while placing it. The jetting action on the wall of the bore hole removes foreign plastering'materia'ls concurrently with the forcing of the chemical treat-- ing agent into the stratum. l

As still another embodiment of the present' invention, an acid soluble plastering material, such as calcium carbonate, may be employed in the drilling fluid, and a sealing agent containing an appreciable amount of acid employed, whereby the acid dissolves any of the solid material which may be deposited on the wall of the bore hole during the injection oi the sealing agent.

I claim:

A method of completing wells comprising the steps of packing oi a predeterminedstratum, removing the mud sheath comprising plastering materials from the wall of the bore hole adjacent said stratum, injecting a plugging agent into the borehole adjacent said stratum and ater the removal of the mud sheat placing a sufficient pressure on said plugging agent to overcome the pressure of the formation and to force it from the borehole into the formation, and simultaneously with the application of said pressure, scraping that portion of wall of the borehole adjacent said stratum from which the mud sheath was previously removed to prevent the accumulation of plastering materials thereon. NEWTON B. DSMUKES. 

